Fiber array ferrule and method of making

ABSTRACT

The array ferrule of the present invention has a main body having a fiber receiving cavity which extends therethrough from a mating face to a rear end. A pair of pin slots is formed in opposing side walls of the main body being precisely located with respect to the fiber receiving cavity. In communication with each pin slot is a retention member slot for receiving a pin retention member. A plurality of fibers is precisely positioned within the fiber receiving cavity and an encapsulant substantially surrounds the fibers to substantially fill the fiber receiving cavity.  
     A method of making the array ferrule begins with providing a ferrule blank having a pair of preformed slots extending inward from the opposing side walls. The blank is precisely aligned on a mandrel which is placed within the fiber receiving cavity. Pin slots are broached in each side surface in the area of the preformed slots to form the ferrule main body. The ferrule main body is then positioned within a ferrule receiving opening of a central fixture such that locating pins of the central fixture are positioned within the pin slots. The fiber receiving cavity is then populated with a plurality of optical fibers which are accurately located using a plurality of combs over the ends of the optical fibers which protrude from the mating face. Finally, the fiber receiving cavity is filled with an encapsulant.

FIELD OF THE INVENTION

[0001] The present invention relates to optical connectors and moreparticularly to an array ferrule and a method of making an array ferrulefor use in such optical connectors.

BACKGROUND OF THE INVENTION

[0002] Communication systems have grown in complexity furthering theneed for greater broadband capabilities. Optical communication systemshave been employed in these communication systems and especially inbroadband systems for meeting the need to transport large quantities ofdata, voice and other types of communications over a relatively compactnetwork. Miniaturization of components in optical communication networksalso continues to be necessary. Accordingly, multi fiber opticalconnectors such as the MT-RJ connector have become increasingly popularbecause of their ability to easily connect a plurality of fibersutilizing a standard form factor within the telecommunications industry.MT-RJ connectors have the capability of terminating a pair or a singlerow array of fibers utilizing a ferrule within the same connectorhousing that was previously used for a fiber pair termination.

[0003] One such connector has been developed by the MT-RJ Allianceincluding the companies of Hewlett-Packard, Fujikura, AMP, Siecor, andUsconec. The MT-RJ connector family utilizes an MT ferrule designed tohold 2, 4, 8, 12 or 16 fibers in a linear array. The MT ferrule is aprecision molded solid part having tapered fiber receiving passagewayswhich are loaded with a ribbon fiber array from a rear end. In line withthe fiber array are a pair of pin receiving holes which are used toalign the ferrule end faces of two mated ferrules. The pin holes must beprecisely located with respect to the array of fiber receiving channelsin order to insure proper alignment and to minimize optical signalattenuation between mated fiber end faces.

[0004] U.S. Patent Application Publication U.S. 2003/0016918 provides amulti fiber optical ferrule having a group of fibers terminated from aribbon and arranged in a linear array. The ribbon is secured into theferrule with epoxy introduced through a transverse window formed in theferrule. Once the epoxy is cured, the fibers are cleaved and polished atthe front end or mating face to complete the ferrule and fiber arrayassembly. The ferrule and fiber array assembly may then be loaded into avariety of connector housings which are part of the MT-RJ or otherconnector systems. Although that publication provides for a multi fiberoptical ferrule having a group of fibers arranged in a linear array, itis desirable to increase the number of fibers which may be terminated bysuch an array ferrule. There is a need, however, to increase the densityof fibers in the array while maintaining the same MT-RJ form factor andhousing. It should be understood that this problem is not limited to theMT-RJ form factor, but that the need for high density extends to manyfiber optic connector families. What is needed is a ferrule and methodwhich is capable of increasing the density of fiber terminations withinan existing optical connector housing.

SUMMARY OF THE INVENTION

[0005] The invention provides an array ferrule for use in a fiber opticconnector. The array ferrule has a main body having a fiber receivingcavity which extends therethrough from a mating face to a rear end. Pinslots are formed in opposing side walls of the main body and areprecisely located with respect to the fiber receiving cavity. Incommunication with each pin slot is a retention member slot forreceiving a pin retention member. A plurality of fibers is preciselypositioned within the fiber receiving cavity and an encapsulantsubstantially surrounds the fibers to substantially fill the fiberreceiving cavity.

[0006] A method of making the array ferrule begins with providing aferrule blank having a pair of preformed slots extending inward from theopposing side walls. The blank is precisely aligned on a mandrel whichis placed within the fiber receiving cavity. Pin slots are broached ineach side surface in the area of the preformed slots to form the ferrulemain body. The ferrule main body is then positioned within a ferrulereceiving opening of a central fixture such that locating pins of thecentral fixture are positioned within the pin slots. The fiber receivingcavity is then populated with a plurality of optical fibers which areaccurately located using a plurality of combs over the ends of theoptical fibers which protrude from the mating face. Finally, the fiberreceiving cavity is filled with an encapsulant which is cured.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The invention will now be described by way of example withreference to the accompanying figures of which:

[0008]FIG. 1 is a perspective view of the array ferrule according to thepresent invention;

[0009]FIG. 2 is a perspective view of a ferrule blank positioned withina broach for broaching the pin slots;

[0010]FIG. 3 is a perspective view of a partially assembled arrayferrule of FIG. 1;

[0011]FIG. 4 is a perspective view of an assembly tool for assemblingthe array ferrule of FIG. 1;

[0012]FIG. 5 is a cross sectional view taken along the line 5-5 of FIG.4;

[0013]FIG. 6 is a partially exploded perspective view of the centralportion of the tool shown in FIG. 4;

[0014]FIG. 7 is a top view of the central portion of the tool in FIG. 4in the first step of a progression which accurately positions the fiberswithin the fiber receiving cavity of the ferrule;

[0015]FIG. 8 is a top view of the central portion of the tool in FIG. 4in the second step of a progression which accurately positions thefibers within the fiber receiving cavity of the ferrule;

[0016]FIG. 9 is a top view of the central portion of the tool in FIG. 4in the final step of a progression which accurately positions the fiberswithin the fiber receiving cavity of the ferrule;

[0017]FIG. 10 is a partial cross sectional view taken along the line10-10 of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The optical array ferrule 10 will first be described generallywith reference to FIG. 1. The major components of the array ferruleinclude a main body 12 which supports pins 44 within pin slots 18.Retention members 46 serve to hold the pins 44 within the pin slots 18.A plurality of optical fibers 40 are positioned within a fiber receivingcavity 22 by an encapsulant 26. The plurality of optical fibers 40terminate along a mating face 14. Each of these major components willnow be described in greater detail with reference to FIGS. 1 and 3.

[0019] Referring first to FIG. 3, the main body 12 will be described ingreater detail. The main body 12 is formed of a molded or cast materialwhich exhibits dimensional stability suitable for temperature cycling ofa given application. Various metallic compounds, plastics or othercomposites are suitable for forming the main body 12. For examplesuitable materials include but are not limited to: Z-2, Z-5, Z-7, AL-6063 or AL-60 61. A mating face 14 is formed on one end of the main body12 and a rear end 16 is located opposite the mating face 14. A flange 15is positioned near the rear end 16. A pair of opposing side surfaces 24extend from the mating face 22 to the flange 15. A fiber receivingcavity 22 extends through the main body 12 between the side surfaces 24from the mating face 14 back to the rear end 16. A pair of pin slots 18are formed in the opposing side surfaces 24 and extend from the matingface 14 to the flange 15. The pin slots 18 are formed and located inprecise relationship to the fiber receiving cavity 22. A retentionmember slot 20 extends rearward from the mating face 14 toward theflange 15 and is in communication with the pin slot 18.

[0020] A plurality of optical fibers 40 may be arranged either as abundle or may emanate from a group of ribbon fibers to form an arraywhich is located within the fiber receiving cavity 22 as shown inFIG. 1. The bundle of optical fibers 40 is terminated within theencapsulant 26 along the mating face 14 as will be described below. Themating face 14 is thereafter processed by cleaving the optical fibers 40and polishing the mating face 14 by well known techniques as will bedescribed below.

[0021] A method of making the array ferrule 10 will now be described ingreater detail with reference to FIGS. 2-10. Referring first to FIG. 2,a blank 11 of the array ferrule 10 is formed by either molding orcasting. It should be noted here that the blank 11 is formed to havepreformed slots 17 extending inward from the opposing side surfaces 24.Each preformed slot 17 extends inward only to the respective retentionmember slot 20. The blank 11 is held by a holding device 56 and is slidover a mandrel 50 such that the mandrel is received within the fiberreceiving cavity 22 from the mating face 14. The mandrel 50 is taperedto precisely position the blank 11. The mandrel 50 is mounted on acarrier 52 which is slidable over rails 58 toward a pair of broaches 54which are precisely located with respect to the mandrel 50. As thecarrier 52 is slid past the broaches 54, precise pin receiving slots 18are cut from the preformed slots 17. The resulting array ferrule mainbody 12 has a pair of pin receiving slots 18 precisely located withrespect to the fiber receiving cavity 22. The main body 12 is now readyfor further assembly to produce the completed array ferrule 10.

[0022] An assembly tool 30 will now be described in greater detail withreference to FIGS. 4-6. Referring first to FIGS. 4 and 5, a table 62 hasa central opening 69 passing between its major surfaces in a centralregion. A central fixture 32 is located over the central opening 69 andis mounted to the table 62 by suitable fasteners 68. The central fixture32 has a pair of locating pins 36 mounted within a ferrule receivingopening 34. Guide slots 70 are provided along a major surface and extendoutward from the central opening 69. Comb mounts 64 are positioned overand are movable within the guide slots 70. A comb holder 66 is mountedon the top of each comb mount 64. A respective comb 38 a, 38 b, 39 a, 39b is mounted to each comb holder 66 utilizing a suitable fastener. Thecomb mounts 64 are slidable toward and away the locating pins 36 suchthat the combs 38 a, 38 b, 39 a, 39 b slide along a top surface 35 ofthe central fixture 32. Guide projections 63 extend downward from thecomb mounts into the guide slots and are slidingly received therein inorder to allow the comb mounts 64 to move in a controlled linear motiontoward and away from the locating pins 36.

[0023] The combs 38 a,38 b, 39 a, 39 b will now be described in greaterdetail with reference to FIG. 6. The combs 38 a, 38 b, 39 a, 39 b areeach formed of a sheet material having a thickness which is preferably amultiple of the optical fiber diameter. For example, this multiple maybe five times or greater in order to accurately position the opticalfibers 40 to be orthogonal to the mating face 14 as will be describedbelow. The comb 38 a has a plurality of long teeth 43 extending towardsand slightly beyond an end 47 to form a fiber receiving area 48 having aplurality of spaces between the long teeth 43. The comb 38 b issimilarly formed of a sheet material and has a plurality of short teeth45 extending outward to a complementary end 49 which is profiled to matewith the end 47. The short teeth 45 interlock between the spaces formedby ends of the long teeth 43 which project beyond the end 47. The comb39 a is oriented orthogonal to the combs 38 a, 38 b and is similarlyformed of a sheet material and features a plurality of long teeth 43extending outward to form a similar fiber receiving area 48. A pair ofalignment tabs 41 also extend outward slightly beyond the free ends ofthe long teeth 43. Each alignment tab 41 has a semi-circular free end.The alignment tabs 41 extend outwardly from a respective referencesurface 51 formed along the outside of each alignment tab 41. The comb39 b is similarly formed of a sheet material and features a plurality ofshort teeth 45 being profiled to interlock in the space formed by thefree ends of the long teeth 43 on the comb 39 a. A pair of alignmentrecesses 42 are formed to be complementary to the semi-circular freeends of the alignment tabs 41. A second reference surface 53 is providedon the outside of each alignment recess 42.

[0024] In assembly, the formed main body 12 is placed within the ferrulereceiving opening 34 such that the locating pins 36 are positionedwithin the pin slots 18 in order to precisely locate the fiber receivingcavity 22 with respect to the combs 38 a, 38 b, 39 a, 39 b. The opticalfibers 40 are then positioned within the fiber receiving cavity 22 asbest shown in FIGS. 6 and 3.

[0025] Alignment of the optical fibers 40 within the fiber receivingcavity 22 will be described in greater detail with reference to FIG. 6and the progression shown in FIGS. 7-9. Referring first to FIG. 7, oncethe optical fibers 40 are roughly aligned within the fiber receivingcavity 22, the combs 38 a and 38 b are moved in the direction shown bythe arrows in FIG. 7 by sliding the comb mounts 64 within the guideslots 70 such that the plurality of optical fibers 40 are aligned inbetween the interlocking long and short teeth 43, 45. Next, as shown inFIG. 8, the third and fourth combs 39 a and 39 b are moved towards eachother in the direction shown by the arrows in FIG. 8 such that theoptical fibers 40 are positioned between the interlocking long and shortteeth 43, 45. Reference surfaces 51, 53 are positioned to engage thelocating pins 36 in order to precisely locate the optical fibers 40 withrespect to the locating pins 36 and the pin slots 18. Once the opticalfibers 40 are precisely positioned within the combs 38 a, 38 b, 39 a, 39b as best shown in FIG. 10, an encapsulant is injected into thepassageway 28 (FIG. 1) through an encapsulant supply tube 72 and allowedto cool in order to fix the optical fibers 40 in precise location withinthe fiber receiving cavity 22. A suitable encapsulant is a metallicmaterial, for example“Cerrocast”, available from several metalsuppliers, such as Canada Metal. It should be understood that otherencapsulants are within the scope of the invention and may besubstituted for the metallic encapsulant. The array ferrule 10 is thenremoved from the ferrule receiving opening 34. The optical fibers 40 arecleaved and the mating face 14 is polished by well known techniques inorder to complete the array ferrule 10.

[0026] The foregoing illustrates some of the possibilities forpracticing the invention. Many other embodiments are possible within thescope and spirit of the invention. For example, the methods of theinvention may be used to create various array configurations of fibersin rectangular or other shaped fiber receiving openings. It is,therefore, intended that the foregoing description be regarded asillustrative rather than limiting, and that the scope of the inventionis given by the appended claims together with their full range ofequivalents.

1. An array ferrule for use in a fiber optic connector comprising: amain body having a fiber receiving cavity extending therethrough from amating face to a rear end, a pair of pin slots formed in opposing sidewalls extending adjacent to and precisely located with respect to thefiber receiving cavity, and a retention member slot being incommunication with each pin slot; a plurality of fibers preciselypositioned within the fiber receiving cavity; and, an encapsulantlocated around the fibers and substantially filling the fiber receivingcavity.
 2. The array ferrule of claim 1 further comprising at least onepin located within one of the pin slots.
 3. The array ferrule of claim 2further comprising a retention member being secured within one of theretention member slots and being in engagement with the pin.
 4. Thearray ferrule of claim 1 wherein the encapsulant is a metallic material.5. (canceled)
 6. (canceled)
 7. (canceled)
 8. (canceled)
 9. (canceled)10. (canceled)
 11. (canceled)
 12. (canceled)
 13. (canceled) 14.(canceled)
 15. (canceled)